While I was trying JPA stuff on Spring Boot I had a "Access to DialectResolutionInfo cannot be null when 'hibernate.dialect' not set" exception. I was using "spring-boot-starter-data-jpa" and everything seemed to be in place but still I was getting this. Later I realized that I did not include my database's dependency. After I added it to my pom the problem was fixed.
postgresql postgresql 9.1-901.jdbc4